Studies of human biology of vanishing primitive societies focus on neurologic development and learning patterns in diverse cultural experiments in the human condition found in such isolated groups. Opportunistic investigation of problems phrased by man in isolation is the basis of approach from which most of our studies evolved: kuru-CJD GSS-FFI, HIV (AIDS), HTLV-I slow virus infections of the CNS, aging and Alzheimer's, VE, ALS/PD, mental disease, toxic neuropathies. Techniques of molecular genetics, biochemistry, immunology, virology, and field epidemiologic, clinical linguistic and behavioral studies in cultural isolates and genetic and/or geographically isolated primitive bands yield more easily interpretable data than in cosmopolitan societies. Data and specimens from expeditions to Micronesia, Melanesia, Polynesia, South America, Asia and Africa were valuable in recent HIV (AIDS), HTLV-I hantavirus, JCV of PML and herpes virus, CMV and EBV studies. Studies on nutrition, reproduction, fertility, age of puberty and aging, genetic distance and pleomorphisms, unusual and odd higher cortical functions in language learning, cognitive styles, computation (calculation without words or numbers) and culturally modified sexual behavior elucidate alternative forms of neurologic functioning for man which we cannot investigate once the natural cultural experiments in primitive human isolates are amalgamated into the cosmopolitan community of man. Foci of high incidence of kuru, ALS/PD, HTLV-I myelopathy, epilepsy, familial parkinsonism, Viliuisk encephalopathy, other CNS degenerations, hysterical disorders, schizophrenia, bipolar psychoses, neoplasms, goiter, cretinism, rheumatoid diseases, diabetes, asthma, chronic lung disease, malaria, filariasis, leprosy, cysticercosis, and other infections in these isolated groups have yielded widely significant discoveries. HFRS caused by hantaviruses in Asia, USSR, Europe and newly recognized hantaviruses in the U.S. are studied. Human evolution and adaptability to high altitude, various climes, variable food supply, mineral deficiencies, toxic exposures and responses to severe diseases or social psychologic stress are studied in appropriate populations. Thus, HTLV-1 and HIV retroviruses as causes of CNS diseases in man were first found and are best studied in isolated or socially segregated groups: high incidence TSP focus in Tuamaco, Colombia; drug-using mothers in Newark, New Jersey; epidemic neuropathy in Cuba. We now have a proto- Melanesian variant of HTLV-I in New Guinea and Solomon Islands, of an archaic origin, not associated with monkeys at least for millenia.